Biomedical Engineering Reference
In-Depth Information
overcooking and burning of the hotdogs was prevented. Use of IR heating for
pasteurization of oysters, Japanese noodles, and secondary pasteurization of boiled
fi sh paste was reported by Sakai and Mao (
2006
). Sheridan and Shilton (
1999
) eval-
uated the effi cacy of cooking hamburger patties by infrared sources at
ʻ
max
of 2.7
ʼ
m
(Mid-IR) and at
m (Far-IR). The far infrared radiation source helped to
achieve target core temperature at a lower surface temperature, with less surface
drying and charring. The gas consumption when using the longer wavelength infra-
red source was reduced by 55 % over that for the shorter wavelength, higher energy
source. Application of infrared heating for the processing of meat and fi shes is not
fully explored and it is expected that the utilization of IR heating in the food pro-
cessing sector, especially in the area of minimal processing of food and meat prod-
ucts will be fully tapped in the near future.
ʻ
max
of 4.0
ʼ
10.2.1.3
Microwave Heating
It refers to the use of electromagnetic waves of certain frequencies to generate heat
in material. Most commonly used microwave frequencies for food applications are
2,450 MHz and 915 MHz. Ionic conduction and dipolar rotations are two major
mechanisms of interaction of foods with microwaves. In ionic conduction, the posi-
tively charged ions accelerate in the direction of the electric fi eld in microwave
oven, while negatively charged ions move in the opposite direction (Sahin and
Sumnu
2006
). Since electric fi eld changes its direction depending on frequency, so
the direction of the motion of the positive and negative ions. Moving particles col-
lide with the adjacent particles and set them into more agitated motion, thus tem-
perature of the particle increases. In the presence of polar molecules, heat generation
in microwave oven takes place by the mechanism of dipolar rotation. When polar
molecules interact with electric fi eld, they try to orient themselves in the direction
of the fi eld and they collide with the other molecules. The change in the direction of
the fi eld results in further collision since they try to line up with the reversed directions,
thus thermal agitation and heating take place (Sahin and Sumnu
2012
). Microwave
heating technique has been used in the thawing, heating, cooking, drying and frying
of foods.
Application in raw products
: Microwave thawing and/or re-heating has signifi cant
advantages over the conventional methods. These include shortening of the thaw-
ing time from hours to minutes, reduction in the plant space devoted to thawing and
the elimination of the requirement for thawing chambers, an increase in the hygienic
conditions and a decrease in the microbial load of the thawed products. Quality
changes of anchovy and bluefi sh thawed by refrigerator, microwave, and running
water were compared by Baygar et al. (
2004
). Microwave thawing prolonged the
spoilage of fi sh. The spoilage of samples thawed in water and a refrigerator took
place after the third thawing process while microwave-thawed samples were spoiled
after the fourth thawing process. In another study, the effect of different thawing
methods such as microwave and refrigerator thawing on quality of shrimp was
